[U-Boot-Users] embedding environment by hand

[Mike Frysinger]

On Monday 15 October 2007, Wolfgang Denk wrote:
> in message <200710150059.20355.rgetz at blackfin.uclinux.org> you wrote:
> > Things are complicated by the fact that this LDR format is not static -
> > and continues to evolve with every new part that comes out, as the person
> > who writes the BootROM decides to add new features, that require new
> > switches and bit fields in the LDR stream.
>
> But it doesn't rip a binary image apart, or does it?  If  it  does  -
> then how do you actually link U-Boot?

it doesnt.  the .bin -> .ldr conversion happens after everything.  we already 
have a utility in u-boot mainline that does this (bin2ldr), ive just 
implemented a more generic version in our svn tree since.

> > We are having problems embedding the U-Boot environment into this ldr
> > file.
>
> Well, then don't embed it - this is not  necessary.  There  are  many
> board  configurations  without  embedded  environment.  Embedding the
> environment makes only sense on certain boards which use boot  sector
> type  flash  chips  where you (1) have to write the U-Boot image to a
> specific location to match the hardware-defined  reset  entry  point,
> and  (2)  you want to use one or more of the smaller boot sectors for
> the environment, but these are now located right  within  the  U-Boot
> image.
>
> As far as I understand your decription,  you  also  have  small  boot
> sectors  you  want  to  use  for  the  environment,  but  no specific
> requirement for the location of U-Boot.

there is a specific requirement for the location of U-Boot.  it *must* be at 
the very beginning of flash (where all the boot sectors are).  the bootrom on 
the Blackfin does not support starting at anywhere else, it will only start 
reading from the very beginning.

> > However, the initial u-boot (elf) is generated without the default
> > environment programmed into it.
>
> Stop. There is probably some confusion here.
>
> U-Boot  always  has  a  default  envrionment  compiled  in.  This  is
> somewhere in the data section and only U-Boot knows where to find it.
> It  gets  used  if  none of the coinfigured environment sectors has a
> valid checksum.
>
> Note that the default environment has *nothing* to do with the
> environment stored in the configured flash sector(s). It is an
> *additional* copy.

i am fully aware of this, but that does not change what i want to do.  by this 
argument, there's no reason to have the tools/envcrc utility in the first 
place.  if it isnt designed specifically for embedding the proper crc-ed 
version into the u-boot image, then it's a useless utility.

> > this would allow the environment.o linked into u-boot.bin to be
> > empty/blank and we can use envcrc helper to extract the environment blob
> > so that the blob can be passed to external utilities for embedding.
>
> If you don't want to embed the environment (or cannot  do  it),  then
> just  don't  do  it.  Configure  as  described above, and use it as a
> separate, detached environment like all the other boards using such a
> configuration.

except that we *do* want to do it and we *can* as outlined already.
-mike
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